Budget physics

Time's Up

Similar timers available from these sources: 
From Amazon: BUY NOW Inverted Timer 

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Time's Up: inverse of the sandglass- tiny plastic beads are less dense than the water and thus ascend to the top of the container under the influence of a buoyant force in accordance with Archimedes' principle. This timer takes almost exactly 6 minutes to complete shown here at normal speed for the first half of this video, and the second half is condensed to 24 seconds in time-lapse. 

Spin Bank

Available from these fine sources: 
From Amazon: BUY NOW: Coin Spin Bank 

Note: this site contains affiliate links for which I may be compensated

Spin Bank: a clever spring mechanism launches each coin into rotation along a symmetry axis on to a concave trapping surface. Angular momentum of the spinning quarter keeps it upright even as it bounces upon impact with the platform. Another spin on making saving spare change fun!